Chemical synthesis is still driven to fit available apparatus and new chemical processes are largely designed and executed without taking into consideration the best reactor configuration or (importantly) scalability for pilot or market scale production. Currently, discovery generally takes place in conventional round flask (or batch) reactors. However, flow reactors are becoming increasingly important in discovery and synthesis of new molecules and processes.
Flow reactors (sometimes called continuous reactors) are in their simplest form tubes along which a fluid is able to flow and within which a reaction is able to take place. They promote the use of continuous processing that is inherently scalable with the potential of seamless transition from discovery to industrial scale production. Although they have been around for a while and a number of supporting studies have been conducted, flow reactors are used very rarely at the moment on a routine basis and only by a small number of laboratories. A number of other laboratory scale reactor designs have been proposed but their use is still very limited with scalability being questionable.
Reactor configurations in current research efforts are largely ad hoc and focused on specific conditions of (for example) temperature and pressure. Because of this specificity, the configurations in question do not easily permit access to a wide range of operating conditions or provide support for studies relating to optimal synthetic route selection and reaction optimisation, without redesign and assembly. Additional apparatus is also required for monitoring, probing, measuring, data collection etc. that must be integrated into the reactor, which typically raises the cost and requires additional effort for integration and calibration. Finally, replication of reported reactions across laboratories is not easy as it requires considerable effort to replicate the reported configuration with substantial consequent trial and error.
A prior art flow reactor is shown in FIG. 1. The oscillatory baffled reactor (OBR) 1 consists of a cylindrical tube 2 in which orifice baffles 3 are placed at equal distance and in which fluid is made to oscillate. This arrangement ensures efficient and controlled mixing and effective heat transfer. Eddies are generated when fluid flow passes through the baffles allowing considerable radial motions, and where actions at the wall are of the same magnitude as they are at the centre of the tube. Uniform mixing in each baffled cell is caused by generation and cessation of eddies, collectively along the tube. This type of reactors have the capability to perform reactions that require long residence times at greatly reduced length-to-diameter ratios and maintain nearly a plug flow pattern. The combination of baffles and the oscillatory motion creates a flow pattern and mixing nearly independent of the net flow at a wide range of values for amplitude and frequency of oscillation. Furthermore, the mixing is sufficient to handle multi phase flows including combinations of gas, liquids and solids as well as slurries allowing the application of this type of reactor to a wide range of applications.
WO 2008/122812 A2 (Nitech Solutions Ltd) discloses such a prior art flow reactor. Specifically, the invention relates to a tubular mixing apparatus and a process for applying oscillatory motion to a mixture. A tubular vessel is equipped with a plurality of annular baffles mounted on rails. Those baffle trains are being provided within the vessel to maintain mixing and dispersion of a substance within the vessel. A plurality of such tubular vessel systems maybe assembled using bends providing an S-shaped or serpentine configuration.
WO 2007/060412 A1 (Nitech Solutions Ltd) teaches a method and apparatus for controlling temperature for the said tubular flow reactor in WO 2008/122812 A3.
WO 2007/065211 (Acqua International Group Inc) discloses a compact reactor which is assembled in the form of modules of individual reactor elements interconnected together. The reactor elements are a selection of straight reactor elements and curved reactor elements of single type or comprising multiple pipes. Alternate straight and curved elements are connected together in a serpentine configuration.
EP 1352686 (Inst. Angewandte Chemie Berlin) discloses a modular process device comprising a row of modular connecting points which are generally cubic in shape for fluidic, electrical, sensor and/or digital material streams. The cubic shape enables the modules to be branched horizontally or vertically in three dimensions.
WO 03/078044 (H2GEN Innovations, Inc) discloses a cross-flow heat exchange reactor including a housing, a plurality of tubes mounted in the housing for carrying a first liquid, and a baffle having a plurality of holes receiving the tubes which is configured to allow second fluid to flow within the housing in a direction generally perpendicular to the tubes.
U.S. Pat. No. 5,586,523 (Bard) discloses a microfluidic modular reactor system which handles fluid volumes in the range of one nanoliter to ten microliters. It is questionable whether this system is scalable to the mesoscale.
US 2002/0045265 (Symyx Technologies Inc) also relates to a microfluidic system, namely a parallel flow reaction system comprising four or more reaction channels. Again, it is questionable how scalable this design is.
US 2006/0224006 A1 (Renewable Products Dev Lab) discloses a process for producing Biodiesel or fatty acid esters from multiple triglyceride feedstocks. The process takes place within three tubular vessels coupled sequentially. Each tubular vessel contains a plurality of static mixing elements.
US2011/0224463 A1 (Zikeli et al.) discloses a modular microreactor system composed of microreactor parts including a plate to accommodate separate reaction tubes with different shapes within which turbulent mixing or reactions can occur. The reaction tubes in that invention are preferably capillaries with an inner diameter of 0.05 mm to 1 mm. The microreactor parts are linked with separate connection elements.